Breast MRI scan

Definition

A breast MRI (magnetic resonance imaging) scan is an imaging test that uses powerful magnets and radio waves to create pictures of the breast and surrounding tissue. It does not use radiation (x-rays).

A breast MRI may be done in combination with mammography or ultrasound. It is not a replacement for mammography.

Alternative Names

How the Test is Performed

You will wear a hospital gown or clothes without metal snaps or a zipper (sweatpants and a t-shirt). Some types of metal can cause blurry images.

You will lie on your stomach on a narrow table with your breasts hanging down into cushioned openings. The table slides into a large tunnel-like tube.

Some exams require a special dye (contrast). Most of the time, you will get the dye through a vein (IV) in your hand or forearm. The dye helps the doctor (radiologist) see some areas more clearly.

During the MRI, the person who operates the machine will watch you from another room. The test lasts 30 to 60 minutes, but may take longer.

How to Prepare for the Test

You may be asked not to eat or drink anything for 4 to 6 hours before the scan.

Tell your health care provider if you are afraid of tight spaces (have claustrophobia). You may be given a medicine to help you feel sleepy and less anxious. Also, your provider may suggest an "open" MRI. The machine is not as close to the body in this type of test.

Before the test, tell your provider if you have:

Brain aneurysm clips

Certain types of artificial heart valves

Heart defibrillator or pacemaker

Inner ear (cochlear) implants

Kidney disease or dialysis (you may not be able to receive the IV contrast)

What Abnormal Results Mean

Risks

MRI contains no radiation. No side effects from the magnetic fields and radio waves have been reported.

The most common type of contrast (dye) used is gadolinium. It is very safe. Allergic reactions to this dye are rare. However, gadolinium can be harmful to people with kidney problems that need dialysis. If you have kidney problems, tell your provider before the test.

The strong magnetic fields created during an MRI can make heart pacemakers and other implants not work as well. It can also cause a piece of metal inside your body to move or shift.

Considerations

Breast MRI is more sensitive than mammogram, especially when it is performed using contrast dye. However, breast MRI may not always be able to distinguish breast cancer from noncancerous breast growths. This can lead to a false-positive result.

MRI also cannot pick up tiny pieces of calcium (microcalcifications), which mammogram can detect.